Interação entre sistemas de produção e bioinsumos no controle da traça-das-crucíferas em couve

Abstract

Brassica oleracea var. acephala, known as collard green, is an important vegetable for human food and cultivated in organic and conventional production systems. However, Plutella xylostella, known as diamondback moth (DBM) is one of the most harmful insects to this crop in the world. Therefore, to reduce damage caused by the insect, chemically synthesized insecticides have been used as the main control tool, however, their misuse leads to negative impacts on the environment and increases populations resistant to some of their active ingredients. Therefore, there are alternatives with lower environmental impact that can complement integrated insect management, such as the use of commercial bioinsecticides. However, a reduction in their effectiveness in the field compared to the laboratory has been reported. Thus, the performance of different bioinsecticides in controlling P. xylostella in collard green production systems was evaluated. In order to determine the mortality of the products prior to spraying in the field, a test was carried out in the laboratory with the treatments neem extract (Azadirachta indica (7.5 mL/L)), a mixture of pyroligneous extract, neem and garlic oil and d-limonene (MEOV (1 mL/L)), Beauveria bassiana (3.5 g/L), mixture of B. bassiana + Metarhizium anisopliae (3.5 g/L), and Shopora flavescens (2.3 mL/L). All the products generated mortalities above 70%, except for MEOV. Consequently, field research was carried out in the municipality of Pato Branco, Paraná, during the summer from September 2023 to February 2024, in three locations planted with the hybrid ’Manteiga’-Gran Crop, each one under three different production systems: organic, in transition and conventional, with three sprays per week of commercial products with the active ingredients: Bacillus thuringiensis isolates 1641 and 1644 (1.2 L/ha), A. indica (1.8 L/ha), MEOV (0.18 L/ha), B. bassiana (1.2 kg/ha), mixture of B. bassiana + M. anisopliae (0.6 kg/ha), and S. flavescens (1.7 L/ha). Hence, the population fluctuation of P. xylostella, the intensity of the damage and their relationship were evaluated. According to the joint analysis of the data, the performance of the bioinsecticides was not influenced by the characteristics of each production system. For the average population fluctuation, differences were found between each of the production systems, (organic: 0.55 individuals/plant, in transition: 1.36 individuals/plant, and conventional: 1.01 individuals/plant), as well as the lowest values for the product S. flavescens: (0.4 individuals/plant), with differences for all the products before and after spraying. In terms of damage intensity, differences were observed between each of the production systems (organic:23.24%, in transition: 35.17% and conventional: 32.69%), in addition to reporting the lowest damage intensity in relation to the control for the products B. thuringiensis: (29.86%), MEOV:(29.86%), A. indica: (28.53%) and S. flavescens: (26.27%), but no differences were found in the intensity of damage before and after spraying. Subsequently, the linear regression model attributed a 53% increment in damage generated by the increase in P. xylostella individuals, with damage intensities above 35% that can generate economic losses when 1.48 individuals are found per plant. Hence, it is hoped that this study will provide a tool on the effectiveness of bioinsecticides in reducing the damage caused by P. xylostella in different collard green production systems.